Current and Future Passenger Diesels

Automakers across the globe have been retooling their passenger diesel powertrains-tweaking fuel injection, timing and combustion specs while adding sophisticated advanced emissions control gear-to meet new U.S. and global regulations on particulate matter and nitrogen oxides.

By Ron Kotrba | August 03, 2007

Diesel passenger vehicles are as prevalent on European roadways as the options for continental consumers are many, but the choices are far more limited to U.S. buyers today. Approximately 63 billion gallons of middle distillate fuels were consumed in the United States in 2005, much of which was used as on-road diesel fuel. But U.S. passenger diesel consumption constituted only a tiny fraction of this. So the biodiesel industry's growth is not constricted at this time by the availability of passenger diesel vehicles. There are good reasons, however, to "dieselize" passenger transport in the United States. The fuel efficiency of a diesel engine compared with an equally sized gasoline counterpart-a savings between 20 percent and 40 percent according to the Diesel Technology Forum-means it consumes less fuel and conserves limited resources. Margo Oge, director of the U.S. EPA's Office of Transportation and Air Quality, calculates that if one-third of all U.S. light-duty vehicles were modern diesels, the United States would consume 1.4 million less barrels of oil per day-an equivalent daily volume of oil imported from Saudi Arabia. Advanced emissions controls such as exhaust gas recirculation (EGR), oxidation catalysts, particulate filters, lean nitrogen oxide traps and selective catalytic reduction (SCR) systems will become standard features to help to make diesels much cleaner compared with those of previous generations. As U.S. car buyers become more attuned to the efficiency and cleanliness of the new-age diesel, consumer demand is expected to rise. The renewable and environmental aspects of biodiesel would naturally intensify the benefits diesel engines offer. Biodiesel would be especially beneficial in the realm of carbon, as diesels already consume less fuel and inherently emit less carbon. Furthermore, as acceptance of light-duty diesels increases, the biodiesel industry would gain the priceless opportunity to build relationships with mainstream consumers, ultimately breeding confidence in the renewable fuel.

Current Diesel Models for the U.S. Market

2006 Volkswagen New Beetle TDIAlthough Volkswagen is not making a 2007 model-year New Beetle TDI (turbocharged direct injection), the company is making the 2006 model of this revisited, revised classic available through this calendar year. The 2006 TDI powertrain consists of a 1.9-liter in-line four-cylinder engine, capable of producing 100 horsepower. Highway driving will achieve 42 miles per gallon (mpg) while city driving is rated at 36 mpg. The German automaker is scrapping production of the 1.9-liter TDI and in 2008 is introducing for the New Beetle a 2.0-liter common-rail diesel engine with 40 more horsepower. "We aren't offering a 2007 model year Jetta or New Beetle due to the fact that that they would not meet the new emissions requirements," says Volkswagen spokesman Steve Keyes. Volkswagen approves the use of B5 under warranty.

2006 Volkswagen Jetta TDIAs is the case with the New Beetle TDI, Volkswagen is not producing a 2007 model-year Jetta TDI. The 2006 model carries the same 1.9-liter diesel engine as the New Beetle TDI, achieving 100 horsepower. Pricing for the stylish auto begins at under $20,000. Future Jettas will come available with a 2.0-liter common-rail diesel engine. The German automaker covers B5 use under warranty.

2007 Volkswagen Touareg TDIIntroduced in 2003, the 2007 Touareg TDI is a sport utility vehicle (SUV) with a 10-cylinder 5.0-liter powerhouse capable of producing 310 horsepower, with maximum torque exceeding 550 pound-feet and towing capacity of more than 7,700 pounds. The automaker states the 2007 Touareg is the first light-duty diesel to come standard with a particulate trap allowing it to meet tightening U.S. emissions regulations. Approved for use of B5, this diesel-powered SUV meets current emissions standards in 45 states.

2007 Jeep Grand Cherokee CRDDaimlerChrysler's Chrysler Group has rolled out for the first time ever a full-sized, diesel-powered SUV-the 2007 Jeep Grand Cherokee CRD. It comes equipped with the same 3.0-liter V6 common-rail injection turbo diesel engine found in the Mercedes Benz GL320, R320 and ML320. Also available in four-wheel-drive, this classic SUV with a new compression ignition twist exhibits a 30 percent fuel economy savings over its gasoline counterpart and produces 20 percent less carbon dioxide emissions. The 3.0-liter diesel V6 is available in the Overland and Limited Cherokee models. The use of B5 is approved and the Jeep Grand Cherokee receives a B5 factory fill.

2008 Audi Q7In 2008, Audi will introduce a 3.0-liter V6 TDI diesel for its Q7 luxury SUV that will meet emissions requirements in all 50 U.S. states utilizing BLUETEC emissions abatement technology in cooperation with DaimlerChrysler. The V6 diesel Q7 will come equipped with common-rail Piezo direct injection fuel delivery system. Audi is also making a monster 12-cylinder 6.0-liter TDI engine for the Q7. According to the automaker, Audi will make more of its vehicles available with diesel engines in the United States as customer demand rises.

2007 Mercedes Benz R320 CDIThis six-passenger luxury vehicle comes with the same quiet and clean 3.0-liter V6 available in the ML320 and GL320. The price of this sleek and roomy addition to the Mercedes Benz family of cars begins at approximately $45,000.

2008 BMWs"Predestined for the U.S. market" is how BMW describes its 3.0-liter variable twin-turbo in-line six-cylinder introduced recently in 335d and 535d European models. With 286 horsepower and 427 pound-feet of torque, the 535d accelerates to 60 mph in less than 6.5 seconds, while delivering an impressive 37 mpg on the highway. The German automaker will fulfill the predestination by bringing its high-tech V6 compression ignition engine to U.S. car markets in 2008.

The Future, Real and ConceptualizedGerman automaker BMW is preparing to launch new diesel passenger vehicles with EfficientDynamics in 2008 U.K. markets, such as the 635d with a twin-turbocharged 3.0-liter. EfficientDynamics is fuel-savings technology that utilizes such things as brake energy regeneration and the ability to decouple the air conditioner from the drivetrain so auxiliary devices don't unnecessarily drag on the engine, all of which combined make for a powerful engine achieving approximately 40 mpg. Other models such as the X5 will be available with EfficientDynamics in U.K. markets in 2008.

Japanese automakers Nissan, Honda, Mitsubishi, Toyota and others intend to come out with clean diesels for U.S. and other markets within the next few years. In April, Nissan announced its plans to launch a clean diesel-powered Maxima line in the United States in 2010. Nissan, which is already supplying Europe with clean diesels, introduced its new Euro 4-compliant two-liter class this year. The company says it will bring clean compression ignition engines to North America, China and Japan. Honda, which produces among other varieties a European Accord with a 2.2-liter i-CTDi engine, states it will bring a similar model to U.S. markets within a couple years, and one that will meet EPA's T2B5 emissions standards. The U.S. model will not only offer high-pressure common-rail injection, reconfigured combustion and timing, and an improved EGR system, but also a dual-layered lean nitrogen oxide trap-a nitrogen abatement technology that doesn't get entwined in the technical and packaging problems of urea injections like some SCR systems. During lean-burn conditions (low-end use), the trap adsorbs nitrogen oxide until rich operating conditions occur when hydrogen from the exhaust reacts with the trapped nitrogen oxide making ammonia, which is then adsorbed in the upper layer. Once lean-burn conditions return, the stored ammonia reacts with exhaust stream nitrogen oxide to make and ultimately emit simple nitrogen. Look for Honda's clean diesels soon.

All automakers have concept cars for the future. Even though Volvo will soon be commercializing diesel hybrids for the heavy-duty markets (see March 2007 Biodiesel Magazine), the talk of passenger diesel-hybrid vehicles has been less than fulfilling. Concepts are often unveiled but commercial costs are still too high. A more realistic concept car, and one more like the Europeans already have available, is a straight-diesel-powered offering by Chevrolet-the Groove. Inspired by a "half-soldier, half-modern" military helmet, the vehicle is powered by a highly efficient 1.0-liter diesel engine.

Developed in collaboration with GM's Saturn and Opel brands, the PreVue concept car-its clever name is an extension of the production-line model compact SUV from Saturn named the Vue-is powered by a two-stage turbocharged 212-horsepower twin-turbo common-rail diesel engine. The automaker states that the PreVue, a three-door four-wheel-drive crossover, merges elements from seemingly contradictory designs of a sporty coupe and a powerful SUV.

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